Sig Sauer M400 TREAD 5.56 NATO AR-15, 16-inch Stainless Threaded Barrel, Free-Float M-LOK Handguard, 30+1
The Sig Sauer M400 TREAD is a feature-forward AR-15 platform rifle built around a 16-inch stainless steel barrel with a 1:8 twist and 1/2x28 threads capped by a 3-prong flash hider. It uses a mid-length gas system and a free-float M-LOK TREAD handguard, paired with a flat-top upper featuring T-marked Picatinny rail. This example is USA-made in Newington, NH and includes a Magpul PMAG and an uninstalled SIG TREAD M-LOK Grip Kit.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: There are light handling marks and some surface scratches visible on the exterior.
What's Included
- Sig Sauer M400 TREAD 5.56mm NATO rifle
- 1 Magpul PMAG Gen M3 30-round AR-15 magazine
- SIG Sauer M400 TREAD / M400 PRO owner's manual
- SIG Sauer TREAD M-LOK Grip Kit (uninstalled)
The 16-inch stainless steel barrel is threaded 1/2x28 and fitted with a 3-prong flash hider. A 1:8 twist supports a broad range of 5.56 NATO loads, while the mid-length gas system and direct impingement action deliver smooth cycling. The trigger is a single-stage design.
The flat-top upper receiver carries a T-marked Picatinny rail, and no iron sights are installed. The free-float aluminum M-LOK TREAD handguard includes an integrated QD sling socket and the TREAD badge, providing modern mounting flexibility while keeping weight down.
Furniture includes a Magpul-branded adjustable carbine stock and a SIG-branded polymer pistol grip with textured panels. Selector markings are pictograms, and the forward assist is not present. Length of pull is listed at 10.5 inches.